package com.lagou.sqlsesstion;

import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import com.lagou.pojo.User;

import java.lang.reflect.*;
import java.util.List;

public class DefaultSqlSession implements SqlSession {

    private Configuration configuration;

    public DefaultSqlSession(Configuration configuration) {
        this.configuration = configuration;
    }

    @Override
    public <E> List<E> selectList(String statementId, Object... params) {
        SimpleExecutor simpleExecutor = new SimpleExecutor();

        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        List<E> eList = (List<E>) simpleExecutor.query(configuration, mappedStatement, params);
        return eList;
    }


    public Object update(String statementId, Object... params) {
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        Object object = simpleExecutor.query(configuration, mappedStatement, params);
        return object;
    }

    @Override
    public <T> T getMapper(Class<?> mapperClass) {
        // 使用JDK动态代理来为Dao接口生成代理对象，并返回

        Object proxyInstance = Proxy.newProxyInstance(DefaultSqlSession.class.getClassLoader(), new Class[]{mapperClass}, (proxy, method, args) -> {
            // 底层都还是去执行JDBC代码 //根据不同情况，来调用selctList或者selectOne
            // 准备参数 1：statmentid :sql语句的唯一标识：namespace.id= 接口全限定名.方法名
            // 方法名：findAll
            String methodName = method.getName();
            String className = method.getDeclaringClass().getName();

            String statementId = className + "." + methodName;

            // 准备参数2：params:args
            // 获取被调用方法的返回值类型
            Type genericReturnType = method.getGenericReturnType();
            // 判断是否进行了 泛型类型参数化
            if (genericReturnType instanceof ParameterizedType) {
                List<Object> objects = selectList(statementId, args);
                return objects;
            }
            if (genericReturnType instanceof User) {
                return update(statementId, args);
            }
            //跟新操作

            return update(statementId, args);
//                return selectOne(statementId, args);

        });

        return (T) proxyInstance;
    }

}
